1. Field of the Invention
This invention relates to an apparatus and method for removing kogation material and foreign material and debris from the heater element of a thermal ink jet printer.
2. Description of the Related Art
Thermal ink jet printers operate by heating a portion of liquid ink until the ink vaporizes, thereby expelling a drop of ink from a printhead onto a recording medium, such as paper. The liquid ink is heated in the printhead by means of a resistive heater, one surface of which is in contact with a supply of the liquid ink held in a heater channel or heater chamber. Occasionally, as the liquid ink is heated and vaporized, the ink will undergo thermal breakdown, resulting in deposits known as "kogation" being formed on the exposed surface of the heater element. Eventually, the kogation builds up to such an extent that it begins to act as an insulator between the heater element and the liquid ink, resulting in poor printer performance. This reduction in performance can cause: 1) an increase in "transit" time and a reduction in drop ejection velocity, resulting in poor drop placement on the recording medium; and 2) a reduction in drop volume, resulting in a loss of ink coverage and image quality.
Because kogation results from a thermal breakdown of the liquid ink, prior attempts to deal with the kogation problem have focused on providing inks that either: 1) would not undergo thermal breakdown; or 2) if the inks would undergo thermal breakdown, would not result in kogation formation. However, due to consumers' demand for full color thermal ink jet printers and page-width printheads at reasonable cost, the use of inks which result in kogation cannot be entirely avoided.
Additionally, deposits of other materials can be left on the heater elements of a thermal ink jet printer during the manufacturing process. These manufacturing materials can include residues from the cleaning and etching processes and excess material deposits from the other layers of the printhead. Regardless of the source, these deposits are difficult to detect during the manufacturing process, difficult to remove using conventional techniques, and can significantly affect print quality. While kogation can be avoided by selection of non-kogating inks, that would have no effect on poor print quality due to foreign material deposits arising from the manufacturing process.